Abstract
Biogenic dimethylsulfide (DMS) is a significant contributor to sulfur flux from the oceans to the atmosphere, and the most significant source of aerosol non sea-salt sulfate (NSS-SO42−), a key regulator of global climate. Here we present the longest running time-series of DMS-water (DMSW) concentrations in the world, obtained at the Rothera Time-Series (RaTS) station in Ryder Bay, West Antarctic Peninsula (WAP). We demonstrate the first ever evaluation of interseasonal and interannual variability in DMSW and associated flux to the atmosphere from the Antarctic coastal zone and determine the scale and importance of the region as a significant source of DMS. Impacts of climate modes such as El Niňo/Southern Oscillation are evaluated. Maximum DMSW concentrations occurred annually in January and were primarily associated with sea-ice break-up. These concentrations resulted in extremely high (up to 968 µmol m−2 d−1) DMS flux over short timescales, which are not parameterised in global-scale DMS climatologies. Calculated DMS flux stayed above the aerosol nucleation threshold of 2.5 µmol m−2 d−1 for 60% of the year. Overall, using flux determinations from this study, the total flux of DMS-sulfur from the Austral Polar Province (APLR) was 1.1 Tg sulfur yr−1, more than double the figure suggested by the most recent DMS climatologies.
Highlights
IntroductionA recent update of the summertime climatology, indicated that extremely high DMS concentrations might be a real feature in some areas of the Southern Ocean[14]; in the short, highly productive Antarctic spring and summer seasons, surface water DMS concentrations can exceed 50 nmol L−1 16–18
Ice type within the bay varied throughout the seasons, as did the extent of the coverage: periods of over 80% sea ice cover were comprised of fast ice with cracks and limited open water; breakup of fast ice to below 50% coverage, and ice movement due to wind and current, resulted in a mix of brash ice of both sea ice and glacial origin and icebergs
In situ concentrations of DMSW and derived DMS flux were compared to those extracted for the Western Antarctic Peninsula (WAP) from existing DMS climatologies, and were significantly higher than models predict during January, the most productive time of the annual cycle
Summary
A recent update of the summertime climatology, indicated that extremely high DMS concentrations might be a real feature in some areas of the Southern Ocean[14]; in the short, highly productive Antarctic spring and summer seasons, surface water DMS concentrations can exceed 50 nmol L−1 16–18. These high values are often associated with the release of ice algae, recognised as a significant source of DMSP19–21, from melted sea ice[21,22,23,24]. Whereas the retreat in sea ice will directly impact on the release of DMSP and DMSP-producing algae, changes in the physical environment can impact indirectly on phytoplankton productivity and composition through changes in light and nutrient availability[32,35]
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